Typhoon Haikui (2023)

Typhoon Haikui, known in the Philippines as Typhoon Hanna, was the first major storm to hit Taiwan since Megi in 2016 and the first typhoon to do so since Nesat in 2017. It also caused serious rainfall in Hong Kong, making it the wettest tropical cyclone to affect the region. Haikui means sea anemone in Chinese. The eleventh tropical storm and eighth typhoon of the 2023 Pacific typhoon season, Haikui began its life as a broad low-pressure area near the Northern Mariana Islands on August 27. The system intensified to a tropical storm the next day and was named Haikui by the Japan Meteorological Agency (JMA), with the Joint Typhoon Warning Center (JTWC) following suit shortly thereafter; PAGASA then named the same system as Hanna when it entered the Philippine area of responsibility. In the succeeding days, Haikui reached severe tropical storm strength and eventually became a typhoon, before making landfall near Taitung City, Taiwan on September 3.

The remnants of Haikui caused torrential rain in Hong Kong as it stalled over Pearl River Delta, resulting in issuing a Black rainstorm signal for 16 hours, the longest duration ever since the rainstorm warning system was implemented in 1992. Haikui also further enhances the southwest monsoon in the Philippines, causing extensive rainfall in Luzon. Overall, Haikui caused US$2.31 billion worth of damages throughout its onslaught.

Meteorological history
While Typhoon Saola was exhibiting a counterclockwise loop east of the Philippines, a new low-pressure area developed into a tropical depression on August 27 near the Northern Mariana Islands. The depression, which was slowly drifting westward, was subsequently upgraded by the JMA into a tropical storm on August 28, naming it Haikui. The JTWC began initiating advisories thereafter and was designated as 10W. Haikui then rapidly strengthened into the severe tropical storm category a few minutes later. Haikui then moved west-northwest and eventually entered the Philippine area of responsibility at around 21:00 PHT (13:00 UTC) and was promptly assigned the domestic name Hanna.

Haikui then maintained its severe tropical storm status for about a day while moving generally westwards across the Philippine Sea, before finally reaching typhoon status on September 1. Haikui then continued westwards over the Philippine Sea with little change in intensity, but later intensified into a Category 2-equivalent typhoon a day later. Haikui later rapidly strengthened into a strong Category 3 typhoon before making landfall over Taitung County, Taiwan, becoming the first storm to hit mainland Taiwan for the first time in 4 years after Severe Tropical Storm Bailu (Ineng), and the first Category 3+ typhoon to hit the island since Typhoon Megi (Helen) in 2016. The collision between Typhoon Haikui & the mountain ranges of Taiwan considerably wrecked the structure of the storm and made it weaken back into a minimal Category 1 typhoon by the time it exited the landmass of the island in the evening. Haikui then moved erratically over the next few hours, heading eastwards and making a second landfall in Kaohsiung, Taiwan. On September 5, Typhoon Haikui made its third and final landfall along the coast of Dongshan County, Fujian as a weakening tropical storm.

Philippines
Though not making any direct landfall in the Philippines, Typhoon Haikui (locally known as Hanna) enhanced the southwest monsoon along with Typhoon Saola and Tropical Storm Kirogi, causing heavy rainfall and strong winds in many areas especially in Luzon, and causing one death. Classes were suspended in some regions including Metro Manila on September 1 in the wake of the three storms that bring heavy rains and gusty winds throughout the country.

Taiwan
Before the arrival of the typhoon, 8,000 people were evacuated from the island, particularly also from the mountainous regions that are prone to landslides.

As Haikui made landfall in Taiwan, it unleashed torrential rains and very strong gusty winds. It left 110,000 of households without power. Two people were slightly injured after a tree fell on a truck in Hualien. Although no deaths were reported, parts of the country experience floods, downed trees, and continued rainfall after Haikui made a second landfall. More than 217,000 households lost electricity in line with the typhoon.

Mainland China
On September 5, Typhoon Haikui made landfall along the coast of Dongshan County, Fujian. A heavy rainstorm occurred in the coastal areas of Fujian, causing the death of two firefighters. Economic losses in Fujian amounted to ¥5 billion (US$683 million).

Land and sea transportation in Guangdong and Huizhou had been suspended due to widespread floods and typhoon prevention. Classes had also been suspended in the cities of Shantou and Chaozhou.

Hong Kong
A low-pressure system associated with Haikui caused flooding in Hong Kong from September 7 to September 8. On September 7, Sha Tau Kok in the North District had already recorded more than 70 mm rainfall by 7 pm, which the Hong Kong Observatory issued a flood warning for Northern New Territories at 7:50 pm. Heavy rainfall then spread to the entirety of the city, and the weather bureau issued the Amber rainstorm signal, which was then upgraded to the Red signal in less than half an hour. At 11:05 pm, the highest warning level, Black rainstorm signal, was issued due to continued worsening situations. It was the first time the warning was issued in two years. It caused three fatalities.

The torrential rainfall continued overnight and into the morning of 8 September, gradually subsiding by afternoon. The Black Rainstorm signal lasted over 16 hours, the longest duration ever since the rainstorm warning system was implemented in 1992. The HKO headquarters accumulated over 632 mm of rainfall within 24 hours, a 24-hour rainfall rate trailing only the record set in May 1889. This also makes Typhoon Haikui the wettest storm in Hong Kong's history, breaking the record of Severe Tropical Storm Sam in 1999. Meanwhile, parts of Hong Kong Island, including Stanley, Chai Wan, Shau Kei Wan and North Point accumulated over 800 mm of rainfall within just 12 hours, the area around Tai Tam even accumulated over 900 mm.

Retirement
Due to heavy damage in China and Taiwan, the Typhoon Committee announced that the name Haikui, along with two others, will be removed from the naming lists and will never be used again as a typhoon name. Its replacement name will be announced in spring 2025.